This invention relates to a building ventilation system and particularly to an inlet flap arrangement which automatically controls air movement through an inlet opening in dependence upon a reduction in pressure within the interior of the building.
In various buildings with particular attention to animal husbandry barns, it is important to maintain air quality at required levels to ensure proper health and survival of the animals contained.
For maximum efficiency it is often required to provide maximum density of animals within the barn and hence the entry of fresh air into the building is essential to maintain the atmosphere within the building at proper levels so as to reduce the concentrations particularly of water vapour and ammonia. By proper introduction of fresh air, the health of the livestock and the operator is protected.
In many cases air control is provided by air extraction fans which pull contaminated air from the interior of the building for direct extraction to the exterior. It is then necessary to replace the extracted air with incoming air. This can of course be achieved merely by providing suitable openings which allow air to flow directly into the interior of the building. However such openings have a number of disadvantages. Firstly the openings cannot be closed and hence air flow cannot be controlled even though the fans may be rendered inoperative. Air movement may continue by way of external air pressure on the building and by way of convection currents. Secondly the air entering into the interior of the building is not controlled in its direction. In this regard it is important in many cases to control the air direction either to ensure that it is properly presented as fresh cooling air directly on to animals that require cooling or in other cases to avoid air being directed straight to animals in such cases where the animals are small and can be killed by excess cooling.
Various designs of inlet duct have been made available and in particular there are provided various arrangements which can be mounted to provide a housing which projects through the wall of the building with the housing possibly including in some cases directional control louvres or plates which direct the air in the particularly required direction either onto or away from the animals as required. Housings of this type in some cases can also include within the housing a flap valve which can open and close automically in dependence upon air pressure across the valve so as to prevent any unwanted backflow of air and also to effectively totally halt the flow of air when no air is required.
However devices of this type have the disadvantage that they are very expensive in comparison with the provision of a simple opening and in large barns of course many such inlet control devices are necessary. Part of this cost penalty is due to the fact that it is necessary to provide a moveable flap valve and in addition to seperately provide control surfaces for guiding the air in the required directions.